Control system



Aug- 25, 1936- v D. R. sHouLTs 1 2,052,256

i CONTROL SYSTEM K' Filed March 5o, 1935 David R. S hou ICs,

His Attorneg.

Patented Aug. 25, 1936 CONTROL SYSTEM David R. Shoults, Scotia, N. Y., assignor to Gen- A eral Electric Company, a corporation of New York 'i Application March 30, 1933, Serial No. 663,527

8 Claims. (Cl. 164-68) 'Ihis invention relates to control systems, more particularly to systems for controlling the opera- -tion of machines having an element operating on a strip of material, and it has for an object the provision of a simple, reliable and eiiicient control system of this character. 4

More specifically the invention relates to systems for controlling the operation of machines in which an element is required to operate in predetermined relationship with the strip of material, such for example as machines for cutting a strip of material into bag lengths or package wrapper lengths in register with designs, labels ,or other matter previously printed on the strips.

In machines of this character which usually consist of a rotary cutting knife and a pair of rolls for feeding the strips to the knife, it is difiicult to maintain the cuts in proper register, even with exactly calculated gear ratios because of variable factors such as slippage, and stretch or shrinkage of the strips due to varying mois- `ture conditions of the atmosphere. These variables are cumulative so that each successive cut is made with greater error. In case the cut is not being made in proper register, it is necessary to compensate for the error.

The ,present invention is an improvement of the invention disclosedin U. `S. Patent No.' 2,002,374, William R. King, filed May 30, 1930 and is also an improvement on the invention disclosed In application Serial No. 589,757, Austyn L. Whiteley, tiled January 29, 1932; and on the invention disclosed in my prior application Serial No. 623,795 filed July 21, 1932. These applications and the King patent are all assigned to the assignee of the present invention, and the inventions thereof were all made prior to the date of the present'invention.

A further and more specific object of this invention is the provision of means for eliminating lhunting, i. e., continued alternate cutting of the strip on opposite sides of the successive desired points of cut-off.

In carrying the invention into effect in one form thereof, a variable speed driving connection provided between the feeding means and the operating element,.and a lever is provided for operating on the variable speed connection, together with means for moving the lever so as to eifect a relatively large correction for the space or positional relationship of the strip and the element, land means for subsequently reducing the amount of movement `of the lever to provide a relatively small. correction for the speed rela.- tionship of the strip and operating element, In

a specific embodiment of the invention, the strip is provided during the printing process with index markings in predetermined relationship with the labels or other printed matter, and suitable light sensitive means controlled by these index 5 markings function through suitable control apparatus to energize an electric motor and cause the latter to move the lever which operates on the variable speed connection and thereby introduce the relatively largeY correction for the l0 space relationship of the strip and operating element, and subsequently centering springs attached to the lever reduce the amount of this correcting movement under the control of a calibrated time delay device,so as to make an l5 ultimate or iinal correction for the relative speeds of the strip and the operating element.

In illustrating the invention lin one form thereof, it is shown as embodied in a system for controlling the cut-oii` operation of a bag cutting or package wrapper cutting machine, but it will be understood that this application of the invention is shown merely for the purpose of illustration and that the invention may be utilized generally for controlling machines having an element for performing various operations on a strip of material in predetermined register with designs, labels, or other matter on the strips.

For a better and more complete understanding of the invention, reference should now be had to the following specifications and to the accompanying drawing in which Fig. 1 is a simple diagrammatic representation of an embodiment of the invention andFig. 2 is a simple diagrammatic representation of a modication.

Referring now to the drawing, a. strip of ma- Hterial I0, such for example as a material from which bag lengths or package wrapper lengths are to be cut, is fed from a supply roll (not shown) over a table II to an element of the machine operating thereon, such asy that represented by the rotary cutting knife I2. Means illustrated as comprising a pa'u` of rolls I3are provided for feeding the strip to the cutting element I2. Th'e strip I0 is provided with designs, 45 labels, or other printed matter (not shown) at each section,'such for example as the section of the strip between the broken line I4 and a similar line obscured by the cutting element I2, at

which lines it is-desired tov sever thestrip for the purpose of lforming articles such as package wrapper lengths or bag lengths upon which the design, label or other matter is properly centered.

The feed rolls I3 are driven by any suitable drivingmeans, such for example as that represented by the electric motor I5 to the drive shaft of which the shaft of the rolls I3 are mechanically connected by gearing I6. As shown, the motor I5 is supplied from a suitable source of power, such for example as that represented by the upper and lower supply lines I1 to which the motor is connected by means of the conductors I8. A motor starting device 20 of any suitable type is included in circuit with the motor.

Likewise the rotary cutting knife I2 may be driven by any suitable driving means, the speed of which may be varied or adjusted to provide for adjustment of the relative operating speeds of the knife and the moving strips so as to cause the knife to operate in a predetermined relationship with respect to the sections of the strip, i. e., to sever the strip at the predetermined cutoif lines Ill. Preferably, however, the cutting knife I2 is driven by the same driving means as those employed to drive the feed rolls I3 and in the drawing, the knife I2 is shown as being driven by the electric motor I5 through a variable speed connection 2I, illustrated as a variable speed transmission device comprising a pair of cone pulleys 22. and 23, connected together by a belt 24, the position of which upon the surfaces of the pulleys is varied by means of a belt shifting device 25. The pulley 22 is xedly mounted on the drive shaft ofthe motor I5 for rotation therewith and the pulley 23 is mounted upon the shaft of the cutting knife I2 so as to rotate therewith.

The belt shifter 25 is actuated by means of a lever 26 to one extremity of which it is connected by means of a connecting link 21. As shown, the lever 26 is provided with a central collar portion 26a, which is pivotally connected to a nut 21, which in turn is actuated in one direction or the other along the screw 28 when the latter is rotated. The lever 26 is fulcrumed in a bifurcated member 30 which as shown is attached by means of connecting rod 3l to the plunger 32 of a retarding device illustrated as an oil dashpot 33. Centering springs 34 and 35 serve to center the lever 26 with respect to the nut 21 and in so doing they eifect movement of the fulcrum point 30.

This lever arrangement serves to provide a correction in the space relationship between the desired cut-off points of the strip I6 and the blade of the rotary cutting knife I2 when such is necessary, and also serves to effect the necessary correction for the relative speeds between thestrips and the cutting knife. Under normal operating conditions the lever26 occupies the upright position in which it is illustrated. If the strip IIJ becomes out of register .with the knife I2,

I the nut 21 is advanced along the screw 28 in the proper direction which effects a movement of the lever 26 about the fulcrum point 36. This movement of the lever effects a relatively large temporary change in the relative speeds of the strip I0 and the knife I2 to compensate for the positional relationship of the strip and the knife. Subsequently the centering springs 34, 35 reduce the amount of movement of the lever 26 by moving the lever 26 in the opposite direction.- .This last mentioned movement of the lever 26 of course changes the position of the original fulcrum point 30 and this movement takes place at a speed determined by the adjustment of the dashpot 33. In its iinal position the lever 26 is again substantially upright as illustrated, and displaced along the screw 28 by an amount proportional to the rotation thereof, thus providing a small and reladuction gearing 31.

tively permanent change inl the relative speeds of the strip and cutting knife I2.

As shown the screw 28 is rotated by a small pilot motor 36 to the driveshaft of which the screw is connected through suitable worm re- The pilot motor 36 is provided with a split series field winding comprising the two oppositely wound portions 36a. and 36h. Energization of the motor through one or the other of these portions of the winding effects operation of the motor in one or the other directions in a well understood manner.

Energization of the pilot motor 36 through one or the other of the oppositely wound portions of its split iield winding is controlled by suitable electromagnetic switching mechanism illustrated as a pair of contactors 38 and 40. The directional contactor 38 when actuated to its upper position serves to connect the pilot motor 36 to a suitable source of power, represented by the two supply lines 4I, in series relationship with the portion 36h of its eld Winding to effect rotation of the motor in a given direction, for example, the forward direction. Similarly operation of the contactar 40 to its 'upper position connects the pilot motor 36 to the source 4I in series relation with the portion 36a of its field lwinding.

As shown in the drawing, the sheet I0 is provided at suitable intervals with indicia or index markings shown as black spots 42 which are .lines I4. No particular relationship between the position of the index markings and the cut-off lines is necessary since it is only required that the same relationship obtain between each 4of the markings and the printed matter or cut-off line with which it is associated.

The operation of the pilot motor 36 to effect the desired correction between the strip IIJ and the cutting knife I2 is automatically controlled by means of the control system illustrated in the drawing as comprising a light sensitive device 43, preferably a photoelectric cell, which responds to the passage of the index marks 42 and a' cooperating selector switch 49 controlled in accordance with the position of the rotary knife I2 to energize one or the other of the electric valves 44, 45 in the respective output circuits of which the operating coils olf the contactors 38 and 40 are connected. As shown, the light sensitive device 43 is mounted above the strip I0 and in such a position with respect to a source of -light 46 as to be influenced by the beam of light reflected from the strip. The light source 46 is illustrated as an ordinary incandescent lamp suitably mounted above the strip and supplied with energy from a suitable source such fdr example as that represented in the drawing by the supply lines IJ to which the lamp is connected by means of the conductors 41. The light sensitive device 43 is so positioned with respect to the rotary knife l2 that one of the index marks 42 interrupts the beam of reflected light to the light sensitive device when one of the cut-ofi lines of the strip I0 is in some predetermined position, for example, when it is at the point of cut-off on the table I I. When one of the index markings 42 is in the position shown with respect to the light source 46 and the light sensitive device 43 shown in the drawabbasso l l:

the light sensitive device'43 is interrupted or at least is greatly diminished, and this interruption or diminution of the received beam of light causes the light sensitive device 43 to produce a controlling impulse', i. e., a change in the magnitude of the current flowing in the electrical circuit 48 in which it is' connected.

Since the limpulses 'produced in the electric circuit 48 when dark spots diminish the light received by the light sensitive device are very feeble, it is necessary to amplify these impulses in order that they may be transmitted and utilized to control the energization of the electric valves 44 and 45. Accordingly, a suitable amplifying device 50 is interposed in the circuit between the light sensitive device 43 and the electric valves 44, 45, and this amplifying device is connected to a suitable electrical source by means of conductors I.

Although the electric valves 44 and 45 may be f of any suitable type, they are preferably of the three electrode type. As illustrated, the valves 44 and 45 are respectively provided with cathodes 44a and 45a, `grids 44h and 45h and plates or anodes 44c and 45o. These valves are also preferably of the type having a small quantity of an inert gas such for example as mercury vapor introduced into their envelopes after exhaust. The presence df this gas Within the envelope serves to convert the usual pure'electron discharge -into an arc stream, the starting of which is controlled by applying a suitable positive bias to the grid and thus constituting the valves electrostatically or grid controlled are rectiers. Once current has started to flow in the anode circuit of this type of valve, it cannot be stopped by control of the grid voltage, but can only be stopped by interrupting the anode circuit or reducing the anode voltage substantially to zero.

The anodes 44e and 45e are respectively connected with the positive side of the direct current lsource 4I in series relationship with the respective operating coils of the directional contactors,

34 and 49.4 Although the controlling impulses produced by the passage of the index marking 42 beneath the light sensitive device 43 are of extremely brief duration, they are nevertheless sufficient to initiate the flow of current 'in' the anode circuit of the electric valve, which current continues to flow `untilthe anode circuit is interrupted. A suitable switching device 52 having a vmagnetic circuit designed to prdvde a time element in its drop out operation serves to interrupt the anode circuit of the electric valves 44 and 45 a predetermined interval of time after the flow of anode current is initiated. Cathodes 44a and 45a of the valves are connected to the negative side of the supply source 4I by means of the conductor 53 with the result that the anodes 44e and 45e are positively biased with respect to the Cathodes, and as shown, the grids 44h and 45h are respectively connected to segments of the selector switch 49 which in turn are respectively connected to sectors 49a' and 49h insulated from each other as illustrated and upon the periphery of which bears a brush 54 connected through the conductor 55 and amplifying apparatus 50 to the circuit of the light sensitive device 43. 'Ihe selector switch 49 is so arranged on the shaft of the rotary knife I2 that the brush 54 is in contact with the insulating portion lbetween the sectors 49a and 49h agli; tlie instant that the index lmark 42 interrupts the beam of light reflected from the i lationship with respect to the strip as to sever it at the proper point of cut-olf. Thus it will be seen that when vthe knife I2 is in correct register with the printed matter on the strip I0, the passage of the index marks 42 to interrupt the light beam received by the light sensitive device 43 does not cause any impulses to be transmitted to the grids 44h and 45h of the electric valves. A

With the above understanding of the elements and the apparatus and their .organization in the completed system, the operation of the system itself will readily be understood from the following detailed description.

`The system is placed in operation by closing the switch 56 to complete an energizing circuit for the operating coil of the time element device 5 2 which circuit is readily traced from the positive side of the supply source 4I through the coil of the time element device 52, the lower contacts of contactors 40 and 38 in their lower positions and thence to the negative side of the supply source 4I. The time element device 52 in responding to the energizati'on of its coil is operated to its upper or closed position in which its contact connects theanodes 44e and 45o to the positive side of the supply source 4I. The driving motor I5 is started by the starting -device 20 and thereafter the 'feed rolls I3 feed the strip I9 to the rotaryknife I2 at therequired rate. As longv as the necessary predetermined relationship exists between theA rotary knife and the printed matter on the strip lll, the index markings 42 interrupt the light beam received by the light sensitive device 43 at the instant that the brush 54 bears upon the insulated portion of the selector switch 49 and no correcting action is made. y

In case the cut is not being made inregi-ster with the printed matter on thestrip, it is necesit is' also necessary to alter the velocity relationship of the rotary knife and the feed rolls toY compensate for the error which rst caused the knife to become out of register with the strip.

Assume for example, that due to some cause the knife becomes out of register with the printed matter on the strip so that the cutis made after the cut-off line has passed the point at the table at which the cut is made. That is to say', the knife is cutting late. 'I'he brush 54 is in contact with the sector 49a at the instant that an index mark 42 interrupts the beam of light received by the light sensitive device and thus an impulse is transmitted through the circuit 48 to the amplifying apparatus 50, which in turn causes a positive bias to be applied to the grid 44h of the electric valve 44. The positive bias applied to the grid of the valve 44 initiates the flow of current in the anode circuitof the electric valve 44, thereby energizing the operating coil of the contactor 40 which in responding to the energization of its coil is operated to its passes out of vcooperative relationship with thelight source 46 and light sensitive device 43, but as previously pointedV out the flow of current in the anode circuit of?I the electric'valve is maintained until the anode circuit is interrupted.

Consequently the contactor-40 remains operated to its upper ;position and the'motor 36 remains energized. The motor 36 rotates the screw 26 in a direction such that the nut 21 is displaced along the screw to the left, as indicated by the arrow. This displacement is comparatively rapid so that the bifurcated member 30 becomes the fulcrum of the lever 26 thereby resulting in a comparatively rapid movement of the belt shifter 25 in a direction such as to increase the speed of the knife l2 with respect to that of the `feed rolls I3. The effect of this rather sudden and large movement of the belt shifter 25 is to provide a rather large temporary correction for the positional relationship of the knife and the strip. It will be seen, however, that if the knife I2 continued to rotate at this substantially increased speed, it would soon become ahead of the strip and would be cutting early instead of late. However, after an interval of time determined by the constants of the time element device 52, the

- contact of the latter due to the deenergization of its operating coil by the upward movement of the contactor 40, descends to its lower position and interrupts the anode circuit of the electric valve 44 with the result that the operating coil of contactor 40 is deenergized. Contactor 40 in responding to the deenergization of its coil descends to the lower position in which it is illustrated and disconnects the motor 36 from the source 4I.

When the lever 26 was rotated in a counter clockwise direction about the fulcrum point 30, the spring 34 was tensioned and similarly the spring 35 was placed under compression. These tensional and compressional forces naturally tend to rotate the lever 26 in the opposite direction, i. e., these forces tend to rotate the lever' 26 in a clockwise direction. The pins by which the collar 26a is attached to the nut 21 now become the fulcrum of the lever 26 and the clockwise rotation of the lever takes place at a speed determined by the adjustment of the dashpot 33. It is seen that as the clockwise rotation of the lever 26 takes place the previous fulcrum 30 is moved in the left-hand direction and this movement continues until the centering springs 34 and 35 move the lever 26 into the upright position in which it is illustrated. It is observed that the clockwise rotation of the lever 26 is opposite to the movement of the lever produced by the motor 36 so that the belt shifter 25 is moved in the right-hand direction to decrease the speed of the knife I2 relative to the roll I3. Thus the relative large change in speed of the knife I2 is considerably reduced. However, the belt shifter 25 is not moved completely back to the position it occupied prior to the initiation of vthe correcting action, but on the contrary is moved to the position it would have occupied had the dashpot 33 and the bifurcated member 30 not provided a fulcrum for the lever 26. Thus finally the lever 26 and the belt shifter 25 come to rest in a position differing from their initial position prior to the initiation of the correcting action by an amount proportional 'to the travel of the nut 21. This amount is just suiiicient to compensate or correct the speed of knife I2 with respect to the strip for the initial error in their relative speeds which initiated the correcting action. This last mentioned correction, i. e., correction for the relative speeds of the knife and the strip is much smaller than the temporary correctionl for the positional relationship and this correction is permanent or relatively permanent in that it endures until the strip and knife have again become out of register and a new correcaceites@ tion is made. 'I'hus the equipment provides a rather large temporary correction and a much smaller permanent correction. As pointed out earlier in the specification, this is the condition that is necessary for stability and the elimination of hunting in a system of this character.

If the rotary knife I2 becomes out of register with the strip I so that the cut is made early instead of late, the brush 54 is in contact with the sector 49h at the instant that the index marking 42 passes beneath the light sensitive device 43, thereby causing a positive bias to be applied to the grid of the valve 45 and in turn energizing the directional contactor 38. Contactor 38 in responding to the energization of its coil moves to its upper position in which it'interrupts the energizing circuit of the time element device 52 and in which it connects the pilot motor 36 to the source 4I in series relationship with the portion 36h of its split field winding, thereby causing this motor to rotate in a direction opposite to that previously described, and causing relative space and relative speed correction between the knife I2 and the strip I0 to be made in the opposite sense to the corrections previously described for the condition in which the knife was cutting late.

In the modification of Fig. 2 the belt shifter 60, the lever 6I, the lever operating motor 62, and the time element device 63 are in all respects similar to Fig. 1. Similarly the light sensitive device, amplifying apparatus, selector switch and electric valve apparatus, which for the purpose of simplicity and avoidance of repetition are omitted from the drawing, are in all respects identical with the apparatus already described in connection with Fig. 1. The system of Fig. 2 differs from that of Fig. 1 primarily in that the dashpot connected to the lever is replaced by two solenoids 64 and 65. These solenoids are attached to the lever 6I near the point where the centering springs 66 and 61 are attached. The contactors 68 and 10 are similar to the contactors 38 and 40 of Fig. 1, but it will be observed that they are provided with additional upper auxiliary contacts 1I and 12 respectively whereby selective energization of the contactors 68, 1U effects selective energization of the solenoids 64, 65. It will be observed lthat the solenoids 64 and 65 are attached to the lever 6I so that they act in opposition. Thus when one or the other of these solenoids isenergized the lever 6I is rotated in a corresponding direction about the fulcrum 13.

In operation, when the strip and the knife become out of register, one or the other of the contactors 68, is energized and operated to its upper closed position in a manner ysimilar to that described in connection with the operation of Fig. 1. Assuming that the contactor 68 is energized, its upper auxiliary contact 1I completes an energizing circuit for the operating coil of solenoid 64 that is traced from the positive side of the supply line 14, conductors and 16, upper contacts of contactor 68, operating coil of solenoid 64 and thence by conductors 11 and 18 to the negative side of the supply line 14. Simultaneously the lower contacts of the contactor 68 in its upper position connect the motor 62 to the source 14 over a circuit that is traced from the positive side of lthe supply line 14 through conductors 15 and 16, lower contact of contactor 68 in the upper position thereof, split ileld winding 62a. armature winding of motor t2l and thence by conductor 'I8 to the opposite side of the supply source 14. In response to the energization of its operating coil the solenoid 64 rotates the lever 6l in a clockwise direction thereby producing the comparatively .large movement of the belt shifter El) and the large temporary correction for the positional relation` ship of the strip and the cutting knife. Simultaneously the motor 62 rotates the screw in such a direction that the nut is displaced along the screw in a, direction toward the right, as indicated by the arrow. This produces the slight additional correctionfor the relative speed of the strip and the knife. 'Ihe clockwise rotation "of the lever 6I places thespring 6l under tension and the spring 66 under compression and these forces of course tend to restore the lever 6I to its original upright position.

The operation of the contactor 68 to its upper position also deenergizes ,the operating coil of the time element device 63 so that after an interval of time determined by the constants of the time element device,- its contact descends to the lower position in which it is illustrated and in which it interrupts the energizing circuit for the operating coil of the contacter 68. As a result of its deenergization the contacter 68 descendsto the lower position in which it is illustrated, thereby deenergizing both the solenoid 64 and the motor 62. The centering springs now rotate'the lever 6l about the fulcrum point 13 in a counterclockwise direction 4and thereby reduce the amount ofthe correction previously made so that the final correction is proportional to the amount that the nut has been displaced along the screw.

'It -will thus be seen that the system in the modification of Fig. 2, like that of Fig. 1, provides both a rather large temporary correction for the positional relationship of the strip and the cutting knife and a small relatively permanent correction for the relative .speeds of the strip and thel knife.

If the strip and the knife had been out of register in the opposite sense of that assumed in` connection with the above descriptionof the operation of the modification to Fig. 2, the contactor 10 would have been energized and the relative space and relative speed corrections between the knife and the strip would have been made in the opposite sense to those above described.

Although in accordance with the provisions of the patent statutes this invention is described as embodied in concrete form, it will be understood that the apparatus'and connections shown and described are merely illustrative and that the invention is not limited thereto since alterations from the true spirit of the invention or thescope of the annexed claims.

What I claim as n ew and desire to secure by actuated by the strip for actuating said member to effect a large temporary correction of the relative speed of said strip and said element, and additional means for causing said member tp reduce said correction to provide a small permanent correction.

2. A control for a device. having an element operating on strip of material and means for feeding the strip to said element comprising a variable speed transmission between said feeding means and element for varying the relative speeds of said feedingmeans and element, Va movable lever operating on the speed changing member of said transmission, means actuated by the relative positions of the strip and element for effecting a movement of said lever to produce a large temporary correction of the relative speeds of said strip and said element, and means for actuating said lever to reduce said correction to provide a small permanent correction. l

3. A control system for a device having an element'operating on a stripof material and means for lfeeding the strip to said element comprising a variable speed driving connection between said feeding means and element for varying the relative speeds of said feeding means and element,

, a movable lever acting on said connection, means and means for subsequently reducing the .amount of movement of said levervthereby to provide a small relatively permanent change in the relative speeds of said element and strip.

4. A control system for a device having an element operating ona strip of material and means for feeding the strip to said element comprising a variable speed driving connection between said feeding means and element for varying the relative speeds of said feeding means and element, a,l lever acting on said variable speed correction and having a. movable fulcrum, means actuated by the relative positions of said strip and element for actuating said lever to make a relatively large temporary correction for the positional relationship of said strip and element and means providing movement of said fulcrum to reduce said correction.

5. A control ysystem for a device havingan element operating on a strip of material and means lpositional relationship of said strip and element and centering springs for effecting movement of f rum to reduce s id orrection r and modifications will readily suggest themselves`- sa'ld me a c to p o to persons skilled in the art without departing vide a iinal correction for the relative speeds of said strip and element, and a time delay device for retarding the movement of said fulcrum.

6. A control system for a device having an element operating on a strip of material and means for feeding the strip to said element comprising an electric motor for driving said feeding means and element, a variable speed driving connection betweenHsaid feeding means-and element for varying the relative speeds thereof, a lever acting on said connection and having a movable fulcrum, light sensitive means actuated by said strip 4and means controlled thereby for moving said lever'to effect a relatively large temporary correction for the positional relationship of said strip and element and means for moving said fulcrum to reduce the amount of movement of said lever and to provide a correction for the relative speeds of said strip and element.

7. A control system for a device having an element operating on a strip of material and means for feeding the strip to said element comprising an electric motor for driving said element and feeding means, a variable speed driving connection between said feeding means and element, a

lever operating on said connection, said lever havl ing a movable fulcrum, an electric motor for moving said lever, means controlled by the relative positions of said strip and element for causing said motor to move said lever' to provide a relatively large temporary correction for the positional relationship of said strip and element, centering spring means for moving said fulcrum to reduce the movement of said lever to provide a reduced correction for the relative speeds of said strip and element, and a dashpot for controlling the rate of movement of said fulcrum.

aosagase an electric motor for driving said feeding means and element, a variable speed driving connection between said feeding means and element f or varying the relative speeds thereof, a lever operating on said connection, a solenoid acting on said lever, a4 motor for actuating said lever, means controlled by the relative positions of said strip and element for energizing said solenoid and said motor to move said lever about its fulcrum to provide a correction for the positional relationship of said V strip and element, a time element device for deenergizing said solenoid after a predetermined interval of time, and spring means for reducing the movement of said lever to provide a correction for the speed relationship of .said strip and element.

DAVID R. SHOULTS. 

